The Gram stain showing Gram-negative diplococci in cerebrospinal fluid (CSF) is characteristic of Neisseria meningitidis, a leading cause of bacterial meningitis in adolescents and young adults.
Step-by-Step Justification:
* Gram Stain Interpretation:
* Gram-negative diplococci in CSF strongly suggest Neisseria meningitidis.
* Classic Symptoms of Meningitis:
* Fever, stiff neck, and vomiting are hallmark signs of meningococcal meningitis.
* Neisseria meningitidis vs. Other Bacteria:
* Haemophilus influenzae (Option A) # Gram-negative coccobacilli.
* Listeria monocytogenes (Option C) # Gram-positive rods.
* Streptococcus pneumoniae (Option D) # Gram-positive diplococci.
CBIC Infection Control References:
* APIC Ready Reference for Microbes, "Neisseria meningitidis and Meningitis".

The correct answer is A, "Pertussis," as healthcare personnel should suspect this condition based on the presented symptoms and the patient's incomplete vaccination history. According to the Certification Board of Infection Control and Epidemiology (CBIC) guidelines, pertussis, caused by the bacterium Bordetella pertussis, is characterized by an initial phase of mild respiratory symptoms (e.g., runny nose, low-grade fever) followed by a distinctive uncontrollable, rapid, and violent cough, often described as a "whooping" cough.
This presentation is particularly concerning in adults with incomplete vaccination histories, as the pertussis vaccine's immunity (e.g., DTaP or Tdap) wanes over time, increasing susceptibility (CBIC Practice Analysis,
2022, Domain I: Identification of Infectious Disease Processes, Competency 1.1 - Identify infectious disease processes). Pertussis is highly contagious and poses a significant risk in healthcare settings, necessitating prompt suspicion and isolation to prevent transmission.
Option B (rhinovirus) typically causes the common cold with symptoms like runny nose, sore throat, and mild cough, but it lacks the violent, paroxysmal cough characteristic of pertussis. Option C (bronchitis) may involve cough and fever, often due to viral or bacterial infection, but it is not typically associated with the rapid and violent cough pattern or linked to vaccination status in the same way as pertussis. Option D (adenovirus) can cause respiratory symptoms, including cough and fever, but it is more commonly associated with conjunctivitis or pharyngitis and does not feature the hallmark violent cough of pertussis.
The suspicion of pertussis aligns with CBIC's emphasis on recognizing infectious disease patterns to initiate timely infection control measures, such as droplet precautions and prophylaxis for exposed individuals (CBIC Practice Analysis, 2022, Domain III: Infection Prevention and Control, Competency 3.2 - Implement measures to prevent transmission of infectious agents). Early identification is critical, especially in healthcare settings, to protect vulnerable patients and staff, and the incomplete vaccination history supports this differential diagnosis given pertussis's vaccine-preventable nature (CDC Pink Book: Pertussis, 2021).
References: CBIC Practice Analysis, 2022, Domain I: Identification of Infectious Disease Processes, Competency 1.1 - Identify infectious disease processes; Domain III: Infection Prevention and Control, Competency 3.2 - Implement measures to prevent transmission of infectious agents. CDC Pink Book:
Pertussis, 2021.

Anoutcome measuretracks the end result of healthcare processes. TheCAUTI rate per 1,000 catheter days directly measures the frequency of infections, making it an ideal outcome metric.
* From theAPIC Text:
"An incidence rate (i.e., the number of new cases during a time period, such as the rate of patients with urinary catheters who get a CAUTI) is a frequently used outcome performance measure."
* Other choices like care compliance or training areprocess measures, not outcomes.
References:
APIC Text, 4th Edition, Chapter 17 - Performance Measures

Group B Streptococcus (Streptococcus agalactiae) is the most common cause of neonatal bacterial meningitis beyond one week of age.
Step-by-Step Justification:
* Group B Streptococcus (GBS) and Neonatal Infections:
* GBS is a leading cause of late-onset neonatal meningitis (occurring after 7 days of age).
* Infection typically occurs through vertical transmission from the mother or postnatal exposure.
* Neonatal Risk Factors:
* Premature birth, prolonged rupture of membranes, and maternal GBS colonization increase risk.
Why Other Options Are Incorrect:
* A. Group A: Rare in neonates and more commonly associated with pharyngitis and skin infections.
* C. Group C: Typically associated with animal infections and rarely affects humans.
* D. Group D: Includes Enterococcus, which can cause neonatal infections but is not the most common cause of meningitis.
CBIC Infection Control References:
* APIC Text, "Group B Streptococcus and Neonatal Meningitis".

The incidence rate is calculated using the formula:
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Why the Other Options Are Incorrect?
* B. (30 ÷ 150,000) × 100 = X - Incorrect multiplier (should be 100,000 for standard incidence rate).
* C. (115 ÷ 150,000) × 100,000 = X - 115 represents total cases (prevalence), not incidence.
* D. (115 ÷ 100,000) × 100 = X - Uses the wrong denominator and multiplier.
CBIC Infection Control Reference
APIC defines the incidence rate as the number of new cases per population unit, typically per 100,000 people.